The present invention relates to a drilling apparatus and method for single pass bolting. More particularly, the present invention relates to a drilling apparatus and method for single pass rock bolting for reinforcement and stabilisation of excavations.
The installation of rock bolts to reinforce excavations is generally currently carried out in two distinct steps. A hole is drilled and the drill steel and bit extracted before the bolt is inserted into the hole and tightened or grouted. Single pass rock bolting involves carrying out these two steps simultaneously, with the task of removing the steel to insert the bolt being eliminated. The advantages of single pass bolting include minimising the time required for bolt installation, improving safety for drilling equipment operators and enhancing prospects for full automation of the process. A further advantage is improved quality and precision of rock bolt installation. The diameter of the hole is critical for rock bolt performance. Presently, differences in the properties of the ground drilled and the use of pre-used bits contribute to poor precision, and reduced -rock bolt performance. Single pass bolting enables an appropriate bit size to be selected for the ground drilled, and thus enables increased precision and improved rock bolt performance.
Prior attempts at single pass bolting have generally been targeted at innovative rock bolts, which also act as the drill steel, having a drill bit provided about an end thereof. Such apparatus are generally used via a rotational drilling method and are generally unsuitable for hard ground conditions. Existing hard ground percussive rock bolts which do not reuse the drill steel suffer from cost problems due to the requirement for water and/or air flushing through the bolt/steel, and the diameter and grade of drilling steel required for drilling through hard rock.
Drill bits adapted to be extracted through a casing are complex and accordingly expensive. Cost competitiveness of drilling speed versus bit cost are complicated in prior single pass rock bolts due to the use of specialised rock bolts and the exclusive use of either complex retractable bits, or expensive disposable bits.
The drilling apparatus and method of the present invention have as one object thereof to substantially overcome the abovementioned problems associated with the prior art, or at least provide an alternative thereto.
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In accordance with the present invention there is provided a drilling apparatus for single pass bolting, the drilling apparatus comprising a drill steel assembly and a disposable drill bit, wherein the drill steel assembly comprises at least a drill steel having first and second ends, the first end of the drill steel being adapted to releasably operatively engage a means for imparting rotational and impact energy and the second end of the drill steel is releasably operatively interconnected with the disposable drill bit, the drill steel being adapted to transmit rotational and impact energy to the disposable drill bit, and wherein the drilling apparatus is characterised in that a portion of the drill steel proximate the second end thereof is adapted to be received within a standard friction bolt, the drill steel assembly is provided with drive means adapted to drive the friction bolt into a body requiring reinforcement, and the drill steel assembly is adapted to allow facile disconnection of the disposable drill bit therefrom, whilst the drilling apparatus is embedded in the body requiring reinforcement.
Preferably, the drive means is provided in the form of a coupling member adapted to releasably receive the first end of the drill steel and the means for imparting rotational and impact energy, wherein the maximum diameter of the coupling member exceeds the diameter of the drill steel.
Preferably still, the coupling member comprises a first bore constructed to releasably receive the first end of the drill steel, and a second bore adapted to releasably receive the means for imparting rotational and impact energy, the head portion of the central bit housing and the aperture through the disposable drill bit are complementary polygonal cross section.
In a highly specific form of the invention, the first end of the drill steel is externally threaded, and the first bore of the coupling member is internally threaded.
In a highly specific form of the invention, the second bore is entemally threaded to match the externally threaded shank adapters of known drill jumbos.
In an alternate form of the invention, the drive means is provided in the form of a flange of diameter exceeding that of the friction bolt. The flange may be integrally provided with the drill steel.
Preferably, the disposable drill bit is of a diameter suitable for installation of the friction bolt in the body to be reinforced.
The drilling apparatus of the present invention may optionally further comprise rotation minimisation means by which rotational energy transmitted from the drill steel to the friction bolt is minimised. In one form of the invention, the rotation minimisation means is provided in the form a washer assembly, wherein at least one lubricated washer is rotatably provided about the drill steel, interposed between the flange of the drill steel and the friction bolt. In a highly preferred form of the invention, the washer assembly comprises two lubricated washers interposed between the flange of the drill steel and the friction bolt.
Preferably, a bore is provided through the drill steel assembly, the bore being adapted to convey water and/or air for flushing drilling debris.
Advantageously from an economic perspective, the disposable drill bit is provided in the form of a single use drill bit, of longevity approximately matched to the depth required for the friction bolt.
In one form of the invention, the disposable drill bit comprises an upper surface studded with teeth in a conventional arrangement, and a lower surface in which is provided a recess, the recess being adapted to directly receive the second end of the drill steel. Preferably, the second end of the drill steel and the recess in the disposable drill bit are of complementary polygonal cross section. Preferably still, the second end of the drill steel and the recess are hexagonal in cross section.
In an alternate form of the invention, the drill steel assembly further comprises a central bit housing adapted to releasably receive the second end of the drill steel and dimensioned to allow the friction bolt to pass thereover, and the disposable drill bit is of substantially annular configuration having an aperture through the centre thereof, wherein the central bit housing is at least partially releasably received through the aperture in the disposable drill bit and is adapted to transmit rotational and impact energy thereto.
Preferably, the central bit housing in turn comprises a head portion, atop which are provided a plurality of teeth, the head portion being adapted to be releasably received through the aperture in the disposable drill bit.
Preferably, the head portion of the central bit housing and the aperture through the disposable drill bit are of complementary polygonal cross section. Preferably still, the head portion of the central housing and the aperture through the disposable drill bit are hexagonal in cross section.
The second end of the drill steel may be of a conventional configuration. In one form of the invention, the second end of the drill steel is threaded, and a complementary threaded recess is provided in the central bit housing.
Preferably, the teeth provided on the head portion of the central bit housing are of a conventional, multiple use type.
In accordance with the present invention there is further provided a drilling apparatus and friction bolt combination, wherein the drilling apparatus comprises a drill steel assembly and a disposable drill bit, the drill steel assembly comprises at least a drill steel having first and second ends, the first end of the drill steel being adapted to releasably operatively engage a means for imparting rotational and impact energy, and the second end of the drill steel is releasably operatively interconnected with the disposable drill bit, the drill steel being adapted to transmit rotational and impact energy to the disposable drill bit, and wherein the drilling apparatus and friction bolt combination is characterized in that a portion of the drill steel proximate the second end thereof is received through the friction bolt, the drill steel assembly is provided with drive means adapted to drive the friction bolt into a body requiring reinforcement, and the drill steel assembly is adapted to allow facile disconnection of the disposable drill bit therefrom, whilst the drilling apparatus is embedded in the body requiring reinforceient.
Preferably, the drive means is provided in the form of a coupling member adapted to releasably receive the first end of the drill steel and the means for imparting rotational and impact energy, wherein the maximum diameter of the coupling member exceeds the diameter of the drill steel.
Preferably still, the coupling member comprises a first bore adapted to releasably receive the first end of the drill steel, and a second bore adapted to releasably receive the means for imparting rotational and impact energy.
In a highly specific form of the invention, the first end of the drill steel is externally threaded, and the first bore of the coupling member is internally threaded.
In a highly specific form of the invention, the second bore is internally threaded to match the externally threaded shank adapters of known drill jumbos.
In an alternate form of the invention, the drive means is provided in the form of a flange of diameter exceeding that of the friction bolt. The flange may be integrally provided with the drill steel.
Preferably, the disposable drill bit is of a diameter suitable for installation of the friction bolt in the body to be reinforced.
The drilling apparatus of the present invention may optionally further comprise rotation minimisation means by which rotational energy transmitted from the drill steel to the friction bolt is minimised. In one form of the invention, the rotation minimisation means is provided in the form a washer assembly, wherein at least one lubricated washer is rotatably provided about the drill steel, interposed between the flange of the drill steel and the friction bolt. In a highly preferred form of the invention, the washer assembly comprises two lubricated washers interposed between the flange of the drill steel and the friction bolt.
Preferably, a bore is provided through the drill steel assembly, the bore being adapted to convey water and/or air for flushing drilling debris.
Advantageously from an economic perspective, the disposable drill bit is provided in the form of a single use drill bit, of longevity approximately matched to the depth required for the friction bolt.
In one form of the invention, the disposable drill bit directly engages the drill steel. The disposable drill bit may comprise an upper surface studded with teeth in a conventional arrangement, and a lower surface. In one form of the invention, a recess is provided in the lower surface of the disposable drill bit, the recess being adapted to directly receive the second end of the drill steel. Preferably, the second end of the drill steel and the recess in the disposable drill bit are of complementary polygonal cross section. Preferably still, the second end of the drill steel and the recess are hexagonal in cross section.
Alternately, a recess may be provided in the second end of the drill steel, said recess engaging a complementary projection in the lower surface of the disposable drill bit. Preferably, the recess and the projection are of complementary polygonal cross section. Preferably still, the recess and the projection are hexagonal in cross section.
In a further alternate form of the invention, the drill steel assembly further comprises a central bit housing adapted to releasably receive the second end of the drill steel and dimensioned to allow the friction bolt to pass thereover, and the disposable drill bit is of substantially annular configuration having an aperture through the centre thereof, wherein the central bit housing is at least partially releasably received through the aperture in the disposable drill bit and is adapted to transmit rotational and impact energy thereto.
Preferably, the central bit housing in turn comprises a head portion, atop which are provided a plurality of teeth, the head portion being adapted to be releasably received through the aperture in the disposable drill bit.
Preferably, the head portion of the central bit housing and the aperture through the disposable drill bit are of complementary polygonal cross section. Preferably still, the head portion of the central housing and the aperture through the disposable drill bit are hexagonal in cross section.
The second end of the drill steel may be of a conventional configuration. In one form of the invention, the second end of the drill steel is threaded, and a complementary threaded recess is provided in the central bit housing.
Preferably, the teeth provided on the head portion of the central bit housing are of a conventional, multiple use type.
In accordance with the present invention there is provided a method for installation of friction bolts into a body requiring reinforcement, the method comprising the steps of:
Simultaneously boring a hole of suitable diameter whilst driving a friction bolt using a drilling apparatus and friction bolt combination, wherein the drilling apparatus comprises a drill steel assembly and a disposable drill bit, the drill steel assembly comprises at least a drill steel having first and second ends, the first end of the drill steel being adapted to receive a means for imparting rotational and impact energy, and the second end of the drill steel is releasably operatively interconnected with the disposable drill bit, the drill steel being adapted to transmit rotational and impact energy to the disposable drill bit, and wherein the drilling apparatus and friction bolt combination is characterized in that a portion of the drill steel proximate the second end thereof is received within a central bore through the friction bolt, the drill steel is provided with drive means adapted to drive the friction bolt into a body requiring reinforcement, and the drill steel assembly is adapted to allow facile disconnection of the disposable drill bit therefrom, whilst the drilling apparatus is embedded in the body requiring reinforcement; and
Retracting the drill steel assembly through the friction bolt, leaving the disposable drill bit in the hole, and the friction bolt in place.